Lessons

General Aptitude
9.1 Numbers - General Questions

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Q.

The sum all even natural numbers between 1 and 31 is:

View Answer

Correct choice: C

Explanation:

Required sum = (2 + 4 + 6 + ... + 30)

This is an A.P. in which a = 2, d = (4 - 2) = 2 and l = 30.

Let the number of terms be n. Then,

tn = 30 ⇒    a + (n - 1)d = 30

⇒ 2 + (n - 1) x 2 = 30

n - 1 = 14

n = 15

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